Pancreatic duct: morphologic and functional evaluation with dynamic MR pancreatography after secretin stimulation

PURPOSE

To assess the utility of dynamic MR pancreatography in the evaluation of the behavior of the pancreatic duct after secretin stimulation and to estimate pancreatic exocrine reserve in patients suspected of having acute recurrent or chronic pancreatitis.

MATERIALS AND METHODS

Ten healthy volunteers and 13 patients suspected of having pancreatic disease and no obvious markers of chronic pancreatitis were studied. Single-shot turbo spin-echo T2-weighted dynamic MR pancreatograms were obtained before and every 30 seconds during the 10 minutes after secretin administration. Morphologic features and diameter of the pancreatic duct were monitored before and during secretin stimulation. Duodenal filling volume was graded. Results were compared with those of endoscopic retrograde cholangiopancreatography and secretin stimulation testing with collection of pancreatic fluid.

RESULTS

Secretin improved the delineation of ductal morphologic features in both groups. Persistent dilatation of the pancreatic duct after stimulation (five patients) was a significant finding (P = .0015) in the diagnosis of papillary stenosis. The mean duodenal filling score was significantly lower in patients with reduced exocrine function (six patients) than that in the volunteers (P < .0001).

CONCLUSION

The use of dynamic MR pancreatography with secretin stimulation may be useful for diagnosing pancreatic papillary stenosis or dysfunction and for detecting reduced pancreatic exocrine reserve.

alpha-Cell neogenesis in an animal model of IDDM

Currently there is debate regarding the capacity of pancreatic islets to regenerate in adult animals. Because pancreatic endocrine cells are thought to arise from duct cells, we examined the pancreatic ductal epithelium of the diabetic NOD mouse for evidence of islet neogenesis. We have evidence of duct proliferation as well as ductal cell differentiation, as suggested by bromodeoxyuridine-labeling and the presence of glucagon-containing cells within these ducts. In addition, the ductal epithelia in diabetic NOD mice expressed the neuroendocrine markers neuropeptide Y and tyrosine hydroxylase. These ducts also expressed the homeobox gene product, insulin promoter factor 1. Ductal cell proliferation and expression of these markers was not observed in transgenic NOD mice (NOD-E), which do not develop clinical or histopathological symptoms of IDDM. This suggests that the observed ductal cell proliferation and differentiation was a direct result of beta-cell destruction and insulin insufficiency in these adult diabetic mice, which further suggests that these events are recapitulating islet ontogeny observed during embryogenesis. It is possible that comparable processes occur in the human diabetic pancreas.

Does high pancreatic duct pressure compromise the duct mucosal barrier function to pancreatic exocrine proteins?

The effect of duct pressure on the barrier function of the pancreatic duct mucosa to both activated and nonactivated pancreatic exocrine enzymes was studied in a feline model. The cat main pancreatic duct was perfused from the tail to the head of the gland with rat pancreatic juice at high duct pressure (40 cm H2O). In a first experiment, nonactivated pancreatic juice was perfused. Analysis of the juice for loss of fluid volume (measurement by weight) and for loss of individual proteins (two-dimensional isoelectric focusing/sodium dodecyl sulphate gel electrophoresis, reversed phase-high performance liquid chromatography) after duct passage showed that pancreatic secretions were completely recovered from the duct lumen. In another experiment, applying the same pressure, the duct was perfused with activated pancreatic juice. Morphologic analysis showed a preservation of the pancreatic duct mucosal integrity immediately after duct perfusion and absence of pancreatic inflammatory lesions 24 h after duct passage. We conclude that the pancreatic duct mucosa is impermeable to the leakage of pancreatic exocrine proteins from the duct lumen at duct pressure < or = 40 cm H2O. Flow of activated pancreatic juice along the pancreatic duct at duct pressure < or = 40 cm H2O does not cause acute pancreatitis. These data do not support the hypothesis that leakage of pancreatic juice from the duct lumen caused by high intraductal pressure due to duct obstruction initiates acute pancreatitis.

Calcium-activated chloride currents and non-selective cation channels in a novel cystic fibrosis-derived human pancreatic duct cell line

The modulation of ion fluxes across the plasma membrane of epithelial cells is central for fluid secretion and absorption. Their disruption can lead to pathological states. An example is cystic fibrosis (CF), a disease characterized by abnormal functioning of the cystic fibrosis transmembrane conductance regulator (CFTR), a cAMP-modulated chloride channel. Here we report the characterization of calcium-activated, DIDS sensitive chloride current and non-selective calcium-activated cation channels in a novel human pancreatic duct cell line (YHV-1) derived from a non-delta F508 mutation CF patient bearing a severe phenotype. Southern blot analysis of the CFTR gene indicates a distinct electrophoretic pattern for the region spanned by exons 15-24, a result presumably related to a mutation which has yet to be identified. In contrast to large calcium-activated chloride currents there were no cAMP-dependent CFTR-type chloride currents. Non-selective cation channels were blocked by intracellular ATP and activated by intracellular calcium and cAMP. We propose the cell line YHV-1 as a suitable model for studying pancreatic ion and fluid secretion alterations in CF.

Purinergic regulation of anion secretion by cystic fibrosis pancreatic duct cells

The present study explored regulation of anion secretion across cystic fibrosis pancreatic ductal epithelium by extracellular ATP with the short-circuit current (Isc) technique. CFPAC-1 cells grown on Millipore filters formed polarized monolayers with junctional complexes as revealed by light and electron microscopy. The cultured monolayers exhibited an increase in Isc in response to apical application of ATP in a concentration-dependent manner (concentration eliciting 50% of maximal response = 3 microM). Replacement of Cl- in the bathing solution or treatment of the cells with a Cl- channel blocker, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), markedly reduced Isc, indicating that a substantial portion of ATP-activated Isc was Cl- dependent. The effects of different adenosine nucleosides and/or nucleotides on Isc were also studied to identify the type of purinoceptors involved. The order of potency, ATP = UTP > ADP > adenosine, was consistent with that for P2 purinoceptors. Reactive blue 2 (100 microM), a P2 antagonist, was found to inhibit 86% of ATP-induced Isc. ATP-induced Isc was also inhibited by pretreatment of the cells with a Ca2+ chelator, 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester (50 microM). Confocal microscopic study also demonstrated a rise in intracellular Ca2+ with stimulation by extracellular ATP, indicating a role of intracellular Ca2+ in mediating the ATP response. ATP-induced Isc was observed in monolayers whose basolateral membranes had been permeabilized by nystatin, which was also sensitive to apical addition of DIDS, suggesting that Isc was mediated by apical Cl- channels. The results of the present study demonstrate the presence of a purinergic regulatory mechanism involving P2U receptor and Ca2+ mobilization in pancreatic duct anion secretion.

Immortalization of bovine pancreatic duct epithelial cells

Pancreatic duct cell lines have been isolated from a number of animal and human tumors, but none appear to express ion transport properties expected for differentiated pancreatic duct epithelial cells. We sought to generate an immortalized ductal cell line from well-differentiated primary cultures of bovine pancreatic duct epithelium. Epithelial cells from the main duct of the bovine pancreas were isolated and immortalized by transfection with a DNA construct encoding simian virus 40 large T antigen. A single clone (BPD1) survived negative selection and was maintained in culture for > 100 passages over 2 yr. The cells grow readily in culture as monolayers and express several properties characteristic of differentiated pancreatic ductal epithelium. The cells do not appear to form a functional tight junction complex, since the transepithelial resistance of the monolayer cultures grown on a permeable support is < 10 omega.cm2. Northern blot analysis revealed that the cells continue to express simian virus 40 large T antigen and contain significant levels of mRNA for proteins thought to be important in transepithelial bicarbonate secretion [carbonic anhydrase II, Cl-/HCO3- exchanger, Na+/H+ exchanger, and cystic fibrosis transmembrane conductance regulator (CFTR)]. In vivo pancreatic ductal secretion is stimulated by the peptide hormone secretin. The secretin receptor is expressed and functionally coupled to adenylate cyclase in the immortalized cells, since secretin caused a dose-dependent accumulation of adenosine 3'5'-cyclic monophosphate (cAMP; approximately 20-fold increase over basal levels) with a mean effective concentration of 15 nM. Elevation of intracellular cAMP by exposure of the cells to forskolin (10 microM) or secretin (0.1 microM) increase plasma membrane Cl- permeability, most likely mediated by activation of CFTR. The results of these studies demonstrate that the pancreatic duct cell line (BPD1) retains several properties exhibited by the secretory epithelial cells that line the pancreatic ductal tree. This cell line should prove useful for studies of expression, function, and regulation of pancreatic duct cell proteins.

Dog pancreatic duct epithelial cells: long-term culture and characterization

Epithelial cells, isolated from a normal dog pancreatic duct, were grown on collagen-coated culture inserts suspended above a feeder layer of myofibroblasts. The cells were examined by transmission electron microscopy, immunohistochemistry, cytogenetics, and flow cytometry. In addition, the constitutive and agonist-stimulated mucin secretion of these cells was studied using a [3H]N-acetyl-D-glucosamine labeling assay, and the stimulation of intracellular cAMP was measured. Cells grown on inserts with a feeder layer developed into confluent monolayers consisting of strictly polarized columnar epithelial cells with prominent microvilli, intercellular junctions, and normal chromosomal characteristics. They could be passaged repeatedly without a detectable alteration in their morphology. The cells could also be grown on organotypic cultures, resulting in further differentiated cells simulating in vivo morphology. Immunohistochemistry demonstrated the presence of carbonic anhydrase II in these cells. Cells treated with vasoactive intestinal peptide, epinephrine, and dibutyryl-cAMP demonstrated a marked increase in mucin secretion compared with controls. In parallel experiments, VIP and epinephrine significantly increased intracellular cAMP. In conclusion we have developed a pancreatic epithelial cell preparation with morphology, cytokinetics, chromosomal, and DNA analyses characteristic of normal cells. Similar to normal columnar epithelial cells, these pancreatic duct cells secreted mucin constitutively and responded to agonist by increasing secretion via a cAMP-mediated pathway. They also contained carbonic anhydrase, which indicates that the cells are capable of secreting bicarbonate.

Enterostatin in gut endocrine cells--immunocytochemical evidence

The presence of enterostatin, a pentapeptide acting as a potential satiety signal in rats, was investigated in rat intestine by immunocytochemical methods. Using antibodies directed against the C-terminal part of enterostatin, the peptide was identified in endocrine cells in the antral part of the stomach and in the small intestine of rat. The immunoreactive cells were more frequent in the antrum and duodenum and became gradually fewer towards the distal small intestine. In some of the labeled endocrine cells, a coexistence of enterostatin with serotonin was revealed by immunocytochemical double staining, implying that the cells were enterochromaffin cells. In the pancreas, no enterostatin-immunoreactive cells were detected, indicating enterostatin to be included in its parent molecule, procolipase. In addition, the existence of procolipase in the gastrointestinal tract, including the pancreas, was investigated. Procolipase immunoreactivity was also identified, except in the pancreas, in chief cells in the fundus region of the stomach. The number of labeled cells declined distally in the stomach, finally being absent in the intestine. Immunoreactive enterostatin was measured with a specific ELISA method. Intestinal content and serum were found to average 540 +/- 70 and 50 +/- 4 nM, respectively. Pancreatic duct ligation strongly reduced the levels of enterostatin in intestinal content to 5.4 +/- 1.5 nM (p < 0.001), and also reduced the serum enterostatin level to 35 +/- 5 nM (p < 0.05). It is concluded that the peptide enterostatin in the rat is produced both in the exocrine pancreas, as part of pancreatic procolipase, and in gut endocrine cells, both sources of peptide being important for the circulating enterostatin.

Duct- to islet-cell differentiation and islet growth in the pancreas of duct-ligated adult rats

We investigated the growth of islet beta and alpha cells in adult rats which had undergone partial pancreatic duct ligation. Whereas the non-ligated head portion of the pancreas remained unaffected in terms of histology and cell population dynamics, the ligated tail part of the pancreas showed pronounced changes in histology and cell growth. These changes included replacement of exocrine acini by ductal complexes and significant growth of islet cells. Using immunocytochemistry and morphometry, we found that the beta-cell population had nearly doubled within 1 week and that a smaller, but also significant growth of the alpha-cell population had occurred. In addition, small islets and islet-cell clusters were more numerous in the pancreatic tail, indicating islet neogenesis. The bromodeoxyuridine (BrdU) pulse labelling index of beta and alpha cells increased five fold and threefold, respectively, in the tail. However, the observed beta-cell labelling index remained below 1% which was largely insufficient to explain the increased number of beta cells. This indicates that recruitment from a proliferating stem-cell compartment was the main source for the beta-cell hyperplasia. A tenfold-elevated BrdU labelling index (18%) was observed in the duct-cell compartment which was identified by specific immunostaining for cytokeratin 20. Transitional cytodifferentiation forms between duct cells expressing cytokeratin 20 and beta cells expressing insulin, or alpha cells expressing glucagon, were demonstrated by double immunostaining. Pancreatic duct ligation also induced the expression of the beta-cell-specific glucose transporter type 2 (GLUT-2) in duct cells, indicating their metaplastic state. We concluded that in this adult rat model, the proliferation and differentiation of exocrine duct cells represents the major mechanism of endocrine beta-cell neogenesis. Our study thus demonstrates that in normal adult rats islet-cell neogenesis can be reactivated by stimulation of pancreatic duct cells.

Changes in the mouse exocrine pancreas after pancreatic duct ligation: a qualitative and quantitative histological study

The pancreatic duct from the splenic lobe, the largest lobe of the pancreas in the mouse, was ligated at 6 weeks of age, with histological and cytological changes in the organ examined 1 day to 16 weeks after the ligation. Changes in the volumes of the pancreatic lobe, exocrine tissue, and interstitial tissue as well as relative total numbers of each cellular element in the organ after duct ligation were stereologically obtained using serial sections of the whole pancreas. Cell sizes, degenerated cell and mitotic cell indices, and nuclear densities of the acinar and ductal cells were also obtained. After duct ligation, the volume of the pancreas increased by interstitial edema in the first 2 days but rapidly decreased thereafter due to atrophy of the exocrine tissue, amounting to 10% or less of normal volume by 7 days. The acinar cells showed an accumulation of the zymogen granules, cytoplasmic condensation and a pyknotic figure of the nucleus; they then were thoroughly deleted with appearance of numerous macrophages. This cell death was suggested to be due to apoptosis. On the other hand, the ductal cells remained in the atrophic pancreas and proliferated with mitotic figures to two times the normal frequency at 3 days, and then formed duct-like structures lacking in the acinar cells. After 2 week, the ductal cells slowly decreased in number also due to cell death, but the pancreas became gradually enlarged by intralobular fatty replacement, to reach a volume approximating that of normal 8 weeks after duct ligation. The stereological method serves for the correct evaluation of cell dynamics including the deletion and proliferation of the cells in the whole organ.

Absorption of triglycerides with defined or random structure by rats with biliary and pancreatic diversion

Fat absorption may be compromised by pancreatic or bile insufficiency, resulting in low uptake of essential fatty acid and energy. Using a rat model of malabsorption, we examined the absorption of defined triglycerides with medium-chain fatty acids (MCFA) in the sn-1,3 positions and essential fatty acids in the sn-2 position (MLM) compared to other fats. The thoracic duct was cannulated for collection of lymph, and the common bile and pancreatic duct was cannulated to divert both the pancreatic juice and bile. The rats were given a single bolus of triglyceride as a taurocholate emulsion. Fat absorption was measured from collected lymph samples. The triglycerides administered were a defined triglyceride, MLM [mainly (8:0/10:0)-(18:2n-6)-(8:0/10:0)], a similar triglyceride subjected to chemical randomization, a mixture of medium-chain triglycerides and soybean oil, and soybean oil, respectively. The first three triglycerides had approximately 36 wt% linoleic acid (18:2n-6) content. Administration of defined triglyceride was followed by significantly higher lymphatic level (wt%) of 18:2n-6 (P < 0.01) as well as a relative enhancement in mol% of 18:2n-6 (P < 0.05) compared to the other triglycerides. Lymphatic absorption of MCFA was similar in the three first groups but not as efficient as for long-chain fatty acids. Our results indicate that defined triglycerides thus may provide a means to increase absorption of essential fatty acids in fat malabsorption, such as that seen in cystic fibrosis, or for pre-term infants.

Bile and pancreatic juice replacement ameliorates early ligation-induced acute pancreatitis in rats

BACKGROUND

In healthy rats, combined bile and pancreatic juice diversion from gut has a synergistic rather than additive effect on stimulation of exocrine pancreatic protein secretion. We hypothesized that exclusion of combined bile and pancreatic juice from gut exacerbates bile and pancreatic-duct ligation-induced acute pancreatitis in rats to a greater extent than exclusion of either bile or pancreatic juice alone.

METHODS

Bile and pancreatic juice (obtained fresh from donor rats) were replaced, separately or together, via a duodenal fistula beginning immediately before 6 hours of duct ligation. Pancreatic morphologic changes were evaluated with an acute pancreatitis histology score and morphometric quantitation of acinar-cell necrosis. Plasma amylase and cholecystokinin concentrations and pancreatic subcellular distribution of cathepsin B activity were determined. Characteristics of bile and pancreatic juice obtained from donor rats were also studied.

RESULTS

Combined bile and pancreatic juice replacement limited the increase in acute pancreatitis histology score by 77%, acinar cell necrosis by 95%, hyperamylasemia by 77%, and hypercholecystokininemia by 99%, while preventing subcellular redistribution of cathepsin B. Amelioration of pancreatic morphologic changes was significantly greater with combined bile and pancreatic juice replacement than with replacement of either bile or pancreatic juice alone.

CONCLUSION

In this experimental corollary of early gallstone-induced acute pancreatitis, combined bile and pancreatic juice exclusion from gut contributes to disease pathogenesis to a greater extent than exclusion of either bile or pancreatic juice alone.

Protein kinase C regulates the magnitude and stability of CFTR currents in pancreatic duct cells

Activation of protein kinase C (PKC) inhibits adenosine 3',5'-cyclic monophosphate (cAMP)-stimulated fluid secretion in rat pancreatic ducts (N. Ashton, R. L. Evans, and B. E. Argent. J. Physiol. Lond. 452: 99P, 1992). Using the patch-clamp technique, we have investigated whether this inhibition of fluid secretion results from an effect of PKC on cystic fibrosis transmembrane conductance regulator (CFTR) Cl channels. Exposure to 100 nM 4 beta-phorbol 12,13-dibutyrate (PDBu) had no effect on CFTR current density in unstimulated duct cells, but caused a 31% increase in the magnitude of CFTR currents recorded from cells stimulated with cAMP. Furthermore, prolonged (2-4 h) exposure of stimulated duct cells to 100 nM PDBu (a condition that should downregulate PKC) significantly slowed the rate at which CFTR currents run down after establishing a whole cell recording. A similar effect was observed with calphostin C (500 nM), a specific inhibitor of PKC. Thus, although inhibition of ductal fluid secretion by PDBu is unlikely to be explained by an effect on CFTR, modulation of PKC activity can affect both the magnitude and stability of CFTR currents in pancreatic duct cells.

Regulation of goblet cell degranulation in isolated pancreatic ducts

Neurohumoral control of goblet cell degranulation in isolated segments of the guinea pig main pancreatic duct was examined using morphometric procedures. Goblet cells represent 25-30% of the epithelial cell population at the head of the main pancreatic duct, a percentage that decreases to 5-10% as the distance from the ampulla increases. Carbachol, bombesin, and vasoactive intestinal peptide (VIP) each stimulated degranulation of duct goblet cells, although cholecystokinin octapeptide, secretin, and histamine did not. The stimulatory effects of carbachol on goblet cell degranulation in isolated pancreatic ducts were blocked by atropine and enhanced by simultaneous exposure to VIP. These observations indicate that goblet cells in guinea pig pancreatic ducts express bombesin, VIP, and muscarinic cholinergic receptors and that multiple intracellular signaling pathways are involved in the regulation of goblet cell degranulation.

Intracellular mediators of goblet cell degranulation in isolated pancreatic ducts

The involvement of particular intracellular signalling pathways in agonist-evoked degranulation of guinea pig pancreatic duct goblet cells was investigated. Carbachol, vasoactive intestinal peptide (VIP), calcium ionophore A23187, phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA), cyclic AMP analogue Sp-5,6-DCl-cBIMPS and forskolin each caused degranulation of goblet cells in isolated ducts. Degranulation induced by carbachol was not inhibited by okadaic acid, cytochalasin-D or nocodazole. These results indicate that at least two major signalling pathways are involved in pancreatic duct goblet cell secretion.

Beta-cell proliferation in normal and streptozotocin-treated newborn rats: site, dynamics and capacity

Regeneration of neonatal beta cells after streptozotocin (STZ)-induced destruction may be due to either replication from pre-existing intra-islet beta cells or extra-islet precursor cells. To further investigate this issue, beta-cell growth was analysed in normal and streptozotocin-treated newborn rats (100 micrograms/g body weight) at several time points during the first 20 days of life. Beta cells were identified by insulin immunostaining, non-isotopic in situ hybridization for rat preproinsulin mRNA, and electron microscopy. Their proliferative activity was recorded by bromodeoxyuridine-pulse labelling. Beta-cell size and total volume were determined by computerized morphometry. In normal rats, there was a threefold increase in total beta-cell volume during the first 5 days of life, with no further expansion till day 20. The bromodeoxyuridine labelling index of the intra-islet beta cells was smaller than that of the extra-islet beta cells (2-3% vs 15-20%). Comparison of the cell birth rate, calculated from the beta-cell labelling index, with the observed increase in beta-cell volume suggested that in normal neonatal rats proliferation of the intra-islet beta-cell population could account for only 10% of the observed expansion. Administration of streptozotocin at birth resulted in more than 90% reduction of the total beta-cell volume at day 2 which then increased to 39% of the normal value by day 20. During this period of partial regeneration, which restored normoglycaemia, the labelling index of intra-islet beta cells was higher than in normal rats (9% vs 2%, p < 0.001), whereas no change was seen in the extra-islet beta-cell labelling index.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects on cellular functions of bile acid and trypsin in stagnant bile juice in anomalous arrangement of the pancreaticobiliary duct

To examine the reasons for the high frequency of biliary tract carcinogenesis in individuals with anomalous arrangement of the pancreaticobiliary duct (AAPBD), we investigated the effects on cellular functions of bile acid and trypsin, which are possible risk factors for carcinogenesis found in stagnant bile juice, using a chick embryo fibroblast culture system. Bile acid was found to increase PGE2 synthesis which has been shown to be increased in premalignant lesions, but to suppress the incorporation of [3H]-labelled TdR into DNA. On the other hand, trypsin increased the incorporation of [3H]TdR into DNA, but did not increase PGE2 synthesis. These results suggest that both the bile acid and trypsin present in the stagnant bile juice in AAPBD act to stimulate cell proliferation, but that their mechanisms of action on cell growth differ. Therefore, the combination of these effects of different types of tumor promoters in the stagnant bile juice in AAPBD may account for the high incidence of carcinogenesis.

[The role of the salivary glands in supporting the relative stability of the blood hydrolytic activity]

Acute and chronic experiments in dogs revealed participation of the salivary glands in ensuring a relative constancy of the blood enzyme activity. The saliva hydrolases reflected the spectrum of blood plasma and its disturbance and extend the possibilities of the sialoenzymodiagnosis.

The effects of feeding and secretin administration on the pancreaticoduodenal papilla of conscious dogs

The aim of this study was to define the functional role of the pancreaticoduodenal papilla (PDP) in the regulation of pancreatic outflow into the duodenum in response to feeding and secretin administration in conscious dogs. The canine model we developed allowed for measurement of the pancreatic ductal pressure and pancreatic outflow simultaneously in a physiological state without interfering with the flow of pancreatic juice via the intact sphincter of the duodenal papilla. Feeding increased the pancreatic outflow from 2.8 +/- 0.2 to 13.4 +/- 1.3 ml/15 min with a slight increase in the pancreatic ductal pressure from 8.5 +/- 0.6 to 13.7 +/- 1.4 cmH2O. The administration of secretin increased the pancreatic outflow from 2.8 +/- 0.2 to 12.7 +/- 1.0 ml/15 min without increasing the pancreatic ductal pressure. The viscosity of the pancreatic juice increased during exposure to food, but decreased following food intake and secretin administration, after which the PDP seemed to dilate by about 40% of the fasting value. The results suggest that PDP changes its opening to maintain the pancreatic ductal pressure below a certain level, even if pancreatic secretion into the pancreatic duct increases due to food intake and secretin administration.

Experimental animal models of acute pancreatitis

Experimental animal models have been employed to study pancreatitis for more than a century. Although not always related to the disease in humans, they have contributed greatly to our current understanding of the pathophysiology and cell biology of this disease. They have also become a standard tool for testing new and promising treatments against pancreatitis. The following article will review the most commonly used experimental models of pancreatitis and some of the lessons we have learned from them.

Pancreatic duct mucosa following bile salt injury in cats. Morphology, barrier function to pancreatic exocrine proteins and vulnerability by activated pancreatic juice

We studied pancreatic duct mucosal morphology and barrier function to both activated and nonactivated pancreatic exocrine proteins following bile salt injury in cats. Prograde pancreatic duct perfusion with 15 mM glycodeoxycholate caused epithelial disruption with focal epithelial loss in the majority of animals. In these cats, flow of preanalyzed nonactivated rat pancreatic juice along the duct resulted in a selective loss of zymogens from the duct lumen as determined by two-dimensional isoelectric focusing-sodium dodecyl sulfate gel electrophoresis and reversed-phase high-performance liquid chromatography. Proteins lost had a low isoelectric point (< or = 5.7) and a molecular weight as large as 47,000 Da and included chymotrypsinogen 1, trypsinogens 1 and 2, and procarboxypeptidases B. Proteins with a high isoelectric point (> 5.7), a high molecular weight (> 47,000 Da), or both, were completely recovered from the duct lumen. Flow of activated rat pancreatic juice along a pancreatic duct with bile salt-induced epithelial disruptions caused additional morphologic alterations including an increase in epithelial destruction and occasional necrosis of the duct interstitial and vascular tissue. In some cats, in which the integrity of the ductal epithelium remained preserved following exposure to the bile salt, neither loss of rat pancreatic exocrine zymogens from the duct lumen nor degradation of the duct mucosa by activated rat pancreatic juice was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of ATP, carbachol and other agonists on intracellular calcium activity and membrane voltage of pancreatic ducts

The pancreatic duct has been regarded as a typical cAMP-regulated epithelium, and our knowledge about its Ca2+ homeostasis is limited. Hence, we studied the regulation of intracellular calcium, [Ca2+]i, in perfused rat pancreatic ducts using the Ca(2+)-sensitive probe fura-2. In some experiments we also measured the basolateral membrane voltage, Vbl, of individual cells. The resting basal [Ca2+]i was relatively high, corresponding to 263 +/- 28 nmol/l, and it decreased rapidly to 106 +/- 28 nmol/l after removal of Ca2+ from the bathing medium (n = 31). Carbachol increased [Ca2+]i in a concentration-dependent manner. At 10 mumol/l the fura-2 fluorescence ratio increased by 0.49 +/- 0.06 (n = 24), corresponding to an increase in [Ca2+]i by 111 +/- 15 nmol/l (n = 17). ATP, added to the basolateral side at 0.1 mmol/l and 1 mmol/l, increased the fluorescence ratio by 0.67 +/- 0.06 and 1.01 +/- 14 (n = 46; 12), corresponding to a [Ca2+]i increase of 136 +/- 22 nmol/l and 294 +/- 73 nmol/l respectively (n = 15; 10). Microelectrode measurements showed that ATP (0.1 mmol/l) hyperpolarized Vbl from -62 +/- 3 mV to -70 +/- 3 mV, an effect which was in some cases only transient (n = 7). This effect of ATP was different from that of carbachol, which depolarized Vbl. Applied together with secretin, ATP delayed the secretin-induced depolarization and prolonged the initial hyperpolarization of Vbl (n = 4). Several other putative agonists of pancreatic HCO3- secretion were also tested for their effects on [Ca2+]i.(ABSTRACT TRUNCATED AT 250 WORDS)

Duodenal wall motility, mucosal net fluid and alkaline secretion in response to luminal acid: role of the vagal nerves and cholinergic transmission

Experiments were performed on chloralose anaesthetized cats. Biliary and pancreatic secretions were diverted by separate cannulation of each duct. A 2-cm segment of the proximal duodenum was isolated between two luminally situated balloons and perfused with isotonic saline containing 14C-PEG 4000 as a non-absorbable marker. The perfusate was analysed with regard to alkalinity (back titration) and concentration of marker (liquid scintillation). Net alkalinization and net fluid transport were calculated with conventional equations. Motor activity in the duodenal wall was recorded as changes in volume of the proximal balloon. Exposing the duodenal segment of 30 mM HCl induced duodenal contractions, net fluid secretion and an increased alkaline secretion, responses which were insensitive to acute truncal vagotomy. The acid-induced increase in contraction frequency was inhibited by hexamethonium, but not by atropine. Alkaline secretion in response to luminal acid was blocked by hexamethonium and inhibited by atropine, whereas the net fluid secretion was insensitive to these compounds. It is concluded that luminal exposure to hydrochloric acid changes the duodenal functional state by mechanisms which are independent of the extrinsic neural supply. Duodenal contractions during luminal acid exposure, and the alkalinization after such acid exposure, are mediated via local neural pathways, involving a nicotinic cholinergic step and, to some degree, muscarinic transmission. The mucosal volume secretion, however, appears to be mediated by non-conventional mechanisms.

Blood pressure reflexes following activation of capsaicin-sensitive afferent neurones in the biliopancreatic duct of rats

1. Inflammatory diseases of the pancreas or diseases which cause obstruction within the biliary or within the biliary or pancreatic duct system are associated with severe pain. Although neuropeptides such as substance P are present in the biliary tree, only few capsaicin-sensitive, substance P-positive nerve fibres have been found in the ducts. In order to obtain functional evidence whether capsaicin-sensitive afferent neurones transmit nociceptive information arising from the biliopancreatic duct, blood pressure reflexes following electrical stimulation of the duct or increases in intraductal pressure were determined in barbiturate-anaesthetized rats. 2. Electrical stimulation of neurones in the biliopancreatic duct was carried out at 30 V, 3 ms, 50 Hz for 20s. In untreated animals the electrical stimulation resulted in rises in blood pressure by up to 25 mmHg, but in about a quarter of all animals tested this response was absent. Following the administration of phentolamine (7 mumol kg-1, i.p.) the blood pressure responses were changed to pronounced and reproducible depressor reflexes of -5 to -30 mmHg. Retrograde injections into the biliopancreatic duct of 300 microliters of a 154 mM sodium chloride solution produced increases in intraductal pressure of approximately 10 mmHg. This elicited shortlasting falls in blood pressure of 3-15 mmHg. Phentolamine significantly augmented the fall in blood pressure to 8-30 mmHg. 3. The depressor reflexes observed in both models after the administration of phentolamine were abolished by morphine (1 mumol kg-1, i.v.). The inhibition by morphine was reversed by naloxone (3 mumol kg-1, i.v.). Naloxone given before morphine did not affect the depressor reflex but prevented the inhibitory action of subsequently injected morphine.4. Acute s.c. injection of capsaicin (30 mg kg-1) abolished the depressor reflexes in response to both types of nociceptive stimulation in phentolamine-treated rats. The initial pressor effects of electrical stimulation were only partly inhibited by capsaicin whereas the basal depressor reflexes in response to elevation of intraductal pressure were abolished. In rats which had received capsaicin on the day before the experiment or had been treated with capsaicin as neonates, only minor rises in blood pressure were induced by electrical stimulation at the beginning of the experiment and no changes in blood pressure occurred after the administration of phentolamine. After adult or neonatal pretreatment with capsaicin the depressor reflexes in response to increased intraductal pressure were only small and were unchanged by phentolamine.5. The depressor reflexes following either electrical stimulation or increases in intraductal pressure were abolished by the unselective Beta-blocker, (-)-propranolol (3 micromol kg-1, i.p.), and greatly reduced by the Beta 1-blocker, metoprolol (6 micromol kg- 1, i.p.). The Beta2-preferring adrenoceptor antagonist, butoxamine(3 micromol kg-1, i.p.), had no effect on the depressor responses. The reflex falls in blood pressure were also abolished by hexamethonium (10 micromol kg-1, i.p.) but not by atropine (3 micromol kg-1, i.p.).6. Both models of stimulation of nociceptive afferents caused identical patterns of blood pressure responses following adrenalectomy or chemical sympathectomy. In adrenalectomized rats, the initial responses consisted of depressor reflexes which were not augmented but significantly reduced by phentolamine and further inhibited by metoprolol. In rats that had been pretreated with 6-hydroxydopamine(total dose 0.6 mmol kg-1) to accomplish chemical sympathectomy, nociceptive stimulation caused rises in blood pressure. Phentolamine treatment abolished these pressor effects but revealed only minor, if any, depressor responses that were unaffected by metoprolol.7. In summary, the hypotensive effects in both models constitute nociceptive reflexes since they are abolished by morphine and restored by naloxone. The afferent part of the reflex is mediated by nerve fibres sensitive to capsaicin. Both experimental procedures seem to elicit two, presumably separate, reflex mechanisms. Firstly, catecholamines released from the adrenal medulla elevate blood pressure or limit hypotensive responses via activation of vascular alpha receptors. Secondly, the reflex inhibition of the sympathetic nerve activity in the heart and the vasculature causes the nociceptive depressor reflexes.

CFTR and calcium-activated chloride currents in pancreatic duct cells of a transgenic CF mouse

We have studied the cystic fibrosis transmembrane conductance regulator (CFTR) and calcium-activated chloride currents in pancreatic duct cells isolated from a transgenic cf/cf mouse created by targeted insertional mutagenesis. Adenosine 3',5'-cyclic monophosphate (cAMP)-activated CFTR chloride currents were detected in 78% (29/37) of wild-type cells, in 81% (35/43) of heterozygote cells, and in 61% (29/47) of homozygous cf/cf duct cells (P > 0.05, cf/cf vs. wild-type and heterozygote). The CFTR current density measured at membrane potentials of +/- 60 mV averaged 22-26 pA/pF in wild-type and heterozygote groups but only 13 pA/pF in cells derived from cf/cf animals (P < 0.05, cf/cf vs. wild-type and cf/cf vs. heterozygotes). In contrast, duct cells from animals of all three genotypic groups exhibited calcium-activated chloride currents that were of similar magnitude and up to 11-fold larger than the CFTR currents. We speculate that these transgenic insertional null mice do not develop the pancreatic pathology that occurs in cystic fibrosis patients because their duct cells contain 1) some wild-type CFTR generated by exon skipping and aberrant splicing and 2) a separate anion secretory pathway mediated by calcium-activated chloride channels.